Field of Invention
The present invention relates to optical imaging, and more particularly to an optical lens assembly applied in a vehicular optical imaging system. The present invention further relates to a manufacturing method of locating a lens unit of the optical lens assembly at an appropriate position.
Description of Related Arts
In general, an optical lens and assembly for optical imaging and, in particular refractive imaging, comprises a lens (or a plurality of lenses) and a base, wherein the lenses allow imaging light to pass therethrough and enable it to be sensed by the sensor and obtaining an imaging photoelectric signal, wherein the base holds the lenses in place to ensure that the optical centers of and the lenses of the optical lens assembly are coaxial and the imaging light can be incident at a desired angle into the lenses. In addition, in order to avoid the and lenses of the lens assembly being directly exposed to the working environment, subject to environmental factors such as water, dust and other effects, thereby reducing the image quality, the existing optical lens assembly generally comprises a casing or a plurality of sealing member to seal the lens assembly. As a result, several problems to be solved in the industrial production of an optical lens assembly are to ensure that the optical axes of the lenses of the lens assembly are coaxial; secondly, to ensure that the light passing through each of the lenses of the lens assembly can be and sensed by the sensor. In other words, the lenses of the optical lens assembly for optical imaging defines an optical axis, and the base of the lens assembly defines a mechanical axis, and only when the mechanical axis and the optical axis are coincided with each other, the imaging light passes through the lenses of the lens assembly is sensed by the sensor to ideally image. Thirdly, as much as possible to improve the sealing effect, to ensure that the image quality is not affected by environmental moisture, dust and so on. In practical industrial production, it is difficult to ensure that the optical axes of the lenses of the optical lens assembly and the mechanical axis of the base of the optical lens assembly are completely overlapped due to and manufacturing and assembly and errors. In some applications, however, it is important to minimize the deviation between the optical axes of the lenses of the optical lens assembly and the mechanical axis of the base of the optical lens assembly to achieve better imaging. For example, in a vehicular optical imaging system, the imaging having a large error may lead to the deviation between the imaging image and the real road conditions, thus affecting the driver's judgment and driving the vehicle. Therefore, in order to obtain a better image quality, it is necessary to minimize the deviation between the optical axes of the lenses of the optical lens assembly and the mechanical axis of the base of the optical lens assembly to obtain high-quality imaging.
As shown in FIG. 1, the conventional optical lens assembly generally has an optical axis A formed by the lenses 1 of the optical lens assembly and a mechanical axis B formed by the fixing base 2 of the optical lens assembly, wherein the fixing base 2 comprises a lens barrel 3, a base 4, a ring 5 and a casing 6, wherein the lenses 1 of the optical lens assembly is preset in the lens barrel 3, and the lens barrel 3 is further provided on the base 4 of the fixing base 2. In addition, in order to hold the lens barrel 3 in a proper position, the fixing base 2 of the optical lens assembly further comprises a pressing ring 5 provided between the casing 6 and the lens barrel 3, wherein the pressing ring 5 is disposed on an outer surface of the lenses 1 so as to locate the lens barrel 3 on the base 4 and coincide the optical axis A of the lenses 1 of the optical lens assembly with the mechanical axis B of the fixing base 2 of the optical lens assembly. In order to seal and prevent water vapor from entering the interior of the optical lens assembly and affecting imaging, the existing optical lens assembly further comprises at least one sealing member (or sealing ring) disposed between the casing 6 and the pressing ring 5 (or base 4) to seal the gap between the casing 6 and the pressing ring 5. That is, the conventional optical lens assembly includes a plurality of independent components and requires a plurality of process steps to assemble and obtain an optical lens assembly having a complete structure. However, the excessive process steps inevitably bring about greater error, and it is difficult to coincide the optical axis A of the lenses 1 of the optical lens assembly with the mechanical axis B of the fixing base 2 of the optical lens assembly. In addition, the excessive process steps further lead to the result that the mechanical axes B of the fixing base 2 of the different optical lens assemblies have different positions, even if they are produced by the same process steps, which further increases the difficulty in coinciding the optical axis A of the lenses 1 of the optical lens assembly with the mechanical axis B of the fixing base 2 of the optical lens assembly. Thirdly, the nonuniformities among the different optical lens assemblies produced by the same process steps further results in difficulty in correcting the errors by utilizing software in a later stage. In addition, since the lenses 1 need to be preset in the lens barrel 3 in advance and preset the lens barrel 3 on the base 4, so an additional sealing structure is necessary to seal the gap between the lens barrel 3 and other structural portions of the fixing base 2. Although the seal between the lens barrel 3 and the base 4 can be enhanced by the screw connection, the glue adhesion and the interference fit, a looseness between the lens barrel 3 and the base 4 is inevitably produced and a deviation between the optical axis A and the mechanical axis B of the optical lens assembly is resulted, the imaging quality of the imaging system using the optical lens assembly is eventually impacted and decreased, with long-term use. Further, the optical lens assembly having a plurality of individual components assembled as described above further requires that the thermal expansion coefficient of the lens barrel 3 and the base 4 is identical, or as close as possible, so as to avoid the tight binding between the lens barrel 3 and the base 4 being broken and the deviation between the optical axis A and the mechanical axis B of the optical lens assembly being produced when environmental temperature changes. Finally, many separate components of existing optical lens assembly require their respective process steps to be fabricated and assembled in multiple steps, which inevitably leads to an increase in the manufacturing cost of the optical lens assembly.